Droplet-generation model could impact upon printing industry

A new model describing the tendency of liquid thread to break into drops could have an impact on printing and other industries.

A team of Cambridge engineers has developed a fully controlled model of a print head to recreate the process of droplet generation.

‘Most conventional print heads will produce very small droplets but only under very specific conditions with a very specific, ink — so if you change the ink properties even by a very small amount most printers will stop working,’ project collaborator Dr Alfonso Arturo Castrejón-Pita told The Engineer.

Indeed one of the greatest challenges facing the printing industry is to develop printheads that are capable of generating ‘clean’ single, uniform-size droplets within a large range of fluid properties, the team says.

Using a very simple fluid solution, made up of water and glycerine, it was able to analyse the effects of viscosity, surface density and density.

The entire process of droplet generation was then recorded using ultrafast-imaging techniques to observe how long threads, or filaments are generated, then broken up.

Project lead Prof Ian Hutchings said: ‘Our regime diagram can predict whether or not a certain liquid can be broken into useful droplets; it is, in simple words, a rule of thumb to determine whether a liquid can be used to produce a droplet or not.’

In addition to traditional printing industries, the knowledge could have a wider impact as Castrejón-Pita explained.

‘People are trying to apply inkjet technology to other industries — biomaterials, electronics, solar cells — for that, of course, we have to understand the physics and dynamics of the whole process. Most of the industry is currently driven by trial and error.’